Drones may be best known for taking impressive aerial videos and inspecting buildings, infrastructure and crops, but they also promise to improve mobile and internet connectivity for emergency services and consumers.

Poor mobile signal in rural areas is frustrating, but it can also be life-threatening in emergency situations. Slow emergency response times mean higher mortality rates.

Mobile signals are usually sent via base stations, attached to buildings or special masts. These are tough to put up in a hurry - so why not attach a base station to a drone?

For the last two years, the Finnish tech firm Nokia and British mobile operator EE have been flying small quadcopter drones mounted with portable mobile base stations in Scotland.

The idea is that in an emergency, a drone could hover over a disaster area to provide instant 4G mobile network coverage with a 50km (31 mile) radius.

But drones can't fly for very long before the battery runs out - 30 minutes is a typical maximum.

So US telecoms giant AT&T is developing a large, helicopter-like drone known as the "Flying COW", short for "Cell on Wings". It is tethered to the ground by a cable that gives it power.

The idea is for fire engines to have their own personal 4G network with a 50km radius.

From the command centre, fire fighters would launch drones and use their cameras to survey the scene. The same concept is being used for search and rescue, with artificial intelligence linking the drones together into a "swarm", so only one pilot is needed to direct a whole group of drones.

Image copyrightGetty ImagesImage caption
A firefighter from a UK fire and rescue service pilots a drone

Nokia is testing out the technology with Vodafone and firefighters in Dusseldorf, Germany.

"You don't need to send firemen into the hostile environment, you will have full situational awareness immediately," says Thorsten Robrecht, Nokia's vice president of advanced mobile networks solutions.

"What we see from the police is that this is much quicker and lower cost than a helicopter, which they still mostly use today."

British start-up Unmanned Life has developed software to send out multiple autonomous drones at the same time to gather information during a crisis, such as when a building is on fire.

One drone hovers in the air providing 4G coverage, while another flies around the building providing live video. A third equipped with heat sensors creates a heat map of the building, while a fourth uses sonar to map structural damage.

Unmanned Life is in talks to provide its system to BT and Verizon, who currently hold government contracts for emergency communication networks in the UK and US.

Swarms of co-operating drones, each with different tasks, help address the flight-time issue because single-function drones can be lighter.

And they can be lighter still if many of their computational and sensing functions - navigation for example - are undertaken by computers on the ground "talking" to the drones wirelessly.

The lighter the drone, the more it can carry.

In February, Ericsson tested this concept with BT and Verizon together with King's College London university in London to show that a drone could autonomously carry 5kg of medical supplies from one location to another, without human intervention.

Image copyrightDavid Tett / EricssonImage caption
A woman watches on a tablet as a man loads a drone with first aid supplies

The trial demonstrated that next-generation superfast 5G networks would be powerful enough to transfer data streams between the drone and the ground, as well as ensuring that the connection to the drone never dropped.